Communications system, infrastructure equipment and method

ABSTRACT

A communications system including an infrastructure equipment, forming part of a mobile communications network, that transmits and receives data to/from a user device via a wireless access interface using a plurality of Orthogonal Frequency Division Multiplexing (OFDM) subcarriers that extend across a first bandwidth. The infrastructure equipment is configured to transmit repeatedly signals representing a same instance of user device payload data in a second bandwidth less than and within a first bandwidth, and includes a subset of the OFDM subcarriers. The user device is configured to receive one or more of the signals repeatedly transmitted across the second bandwidth, to store in a memory signals representing the repeatedly transmitted signals received across the second bandwidth and to combine the stored signals, and to detect the user device payload data from the combined signals, the user device having been provided with an indication of the second bandwidth.

FIELD OF THE INVENTION

The present invention relates to communications systems andinfrastructure equipment for transmitting and receiving data, andmethods of transmitting and receiving data.

BACKGROUND OF THE INVENTION

Fourth generation mobile telecommunication systems, such as those basedon the 3GPP defined UMTS and Long Term Evolution (LTE) architecture areable to support more sophisticated services than simple voice andmessaging services offered by previous generations of mobiletelecommunication systems.

For example, with the improved radio interface and enhanced data ratesprovided by LTE systems, a user is able to enjoy high data rateapplications such as mobile video streaming and mobile videoconferencing that would previously only have been available via a fixedline data connection. The demand to deploy fourth generation networks istherefore strong and the coverage area of these networks, i.e.geographic locations where access to the networks is possible, isexpected to increase rapidly.

The anticipated widespread deployment of fourth generation networks hasled to the parallel development of a class of devices and applicationswhich, rather than taking advantage of the high data rates available,instead take advantage of the robust radio interface and increasingubiquity of the coverage area. Examples include so-called machine typecommunication (MTC) applications, which are typified by semi-autonomousor autonomous wireless communication devices (i.e. MTC devices)transmitting and receiving small amounts of data on a relativelyinfrequent basis. Examples include so-called smart meters which, forexample, are located in a customer's house and periodically transmitinformation back to a central MTC server data relating to the customersconsumption of a utility such as gas, water, electricity and so on.

The nature of MTC devices may lead to their disposal in locations wherecommunication with mobile telecommunications systems such as thosementioned above may prove unreliable, even when taking into accountincreasing coverage. For instance, MTC devices such as smart meters maybe located in the basement of a house or other hard to reach locationswhere signals from mobile telecommunications system may not be receivedat a sufficient strength because they have propagated over highlyattenuating channels. Consequently, devices such as smart meters may beunable to perform reliable detection and estimation of data conveyed bythe signals. Scenarios such as this may also occur when devices are nearthe border of a geographic area served a by mobile telecommunicationssystem. Overcoming these problems by further extending the coverage ofmobile communications networks would allow an increased number ofdevices to be supported by mobile communications networks.

The use of decreased coding rates and reduced order modulations schemespresent a potential solution to improving the reliability of detectionand estimation of data at a device. However, often a restricted set ofpossible modulation and coding rates are supported by devices,especially low cost ones such as MTC devices, and therefore improvementvia coding changes may be limited. Recently it has been suggested thattransmission repetition may present an alternative solution to extendingcoverage to mobile devices which are currently unable to be reliablyserved by a mobile communications network.

SUMMARY OF THE INVENTION

According to an example embodiment, there is provided a communicationssystem comprising an infrastructure equipment for forming part of amobile communications network where the infrastructure equipment isarranged to transmit and receive data to and from a user device via awireless access interface. The wireless access interface is provided bythe infrastructure equipment using a plurality of Orthogonal FrequencyDivision Multiplexing (OFDM) subcarriers and the plurality of OFDMsubcarriers extend across a first bandwidth. The infrastructureequipment is configured to transmit repeatedly signals representing asame instance of user device payload data in a second bandwidth, wherethe second bandwidth is less than and within the first bandwidth andincludes a subset of the OFDM subcarriers. The user device is configuredto receive one or more of the signals repeatedly transmitted across thesecond bandwidth, to store in a memory signals representing therepeatedly transmitted signals received across the second bandwidth andto combine the stored signals. The user device is also configured todetect the user device payload data from the combined signals, where theuser device has been provided with an indication of the secondbandwidth.

According to another example embodiment, the infrastructure equipment isconfigured to transmit repeatedly signals representing a same instanceof user device control data in the first bandwidth, the user devicecontrol data providing an indication of a location of the signalsrepresenting the user device payload data in the second bandwidth. Theuser device is configured to receive one or more of the signalsrepresenting the user device control data repeatedly transmitted acrossthe first bandwidth, to store in the memory signals representing therepeatedly transmitted signals received across the first bandwidth, andto combine the stored signals representing the repeatedly transmittedsignals received across the first bandwidth. The user device is alsoconfigured to detect the user device control data from the combinedsignals representing the repeatedly transmitted signals received acrossthe first bandwidth, where the detection of the user device payload datafrom the combined signals received across the second bandwidth is basedon the indication of the location of the signals representing the userdevice payload data in the second bandwidth.

Repeating transmissions of signals representing user device payload dataenables a user device which is unable to detect and estimate userpayload data from a single instance of the signal, to combine multiplesignal instances I. The combined signals may then be utilised toincrease the strength of the received signal or provide additionalcoding bits and therefore improve an accuracy of the subsequent dataestimation. The repetition of signals representing a same instance ofdata provides an alternative to decreasing a coding rate and ormodulation order of data when attempting to increase the accuracy ofdata detection and estimation at a receiver of a user device whenattempting, for example, to increase the coverage of a mobile network.The use of repetition may be useful for example, when it is not possibleto alter coding rates or modulation orders or they can not be furtherreduced because of compatibility requirements within a system Repetitionmay also present an alternative to coding rates changes, when thecapabilities of intended receiving devices are limited. For instance, amachine type communications (MTC) device may be unable to performcomplex decoding procedures but can receive multiple instance of signaland combine the received signals. Transmitting repetitions of signalsrepresenting user device payload data within a second bandwidth which isless than and within the first system bandwidth reduces the signals thata user device is required to store and combine when the location ofsignals representing the user device payload data within the secondbandwidth is not yet known. For instance, before user device controldata has been detected and estimated, the user device is required tostore signals from the second bandwidth as opposed to across the firstbandwidth. This approach therefore reduces memory requirements at theuser device for storing repeated signals representing user payload datawhilst still allowing the storage and accumulation of the signalsrepresenting the user device control data and the user device payloaddata to be substantially concurrent, therefore reducing the acquisitiontime of the user device payload data.

The expression “signals representing a same instance of user devicepayload data or user device control data” is used to include varioustechniques for transmitting data which represent the same user data,which can be combined to increase the likelihood of correctly recoveringthe user data. In one example the repeated transmission of the signalsrepresenting the user data is a repetition of the same signals. In otherexamples the user data may be encoded so that incremental redundancy canbe used in which an amount of parity of codeword digits are increased bythe repeated transmission of the signals, such that the repeated signalsmay be different.

According to another example embodiment, the wireless access interfaceprovided by the plurality of OFDM subcarriers is divided into aplurality of time periods and the repeated signals representing the userdevice payload data are transmitted in a same set of resources of thewireless access interface in a first time period and in a second timeperiod.

Repeating of signals representing the user device payload data in thesame set of resources within different time period means that thechannel over the signals propagate may be substantially similar andtherefore may simplify the combining of the signals. It may also bebeneficial because the user device is only required to detect andestimate data from a particular portion of the second bandwidth.

According to another example embodiment, the infrastructure equipment isconfigured to transmit the indication of the second bandwidth to theuser device prior to the repeated transmissions of the signalsrepresenting the user device control data.

Transmitting an indication of the second bandwidth to the user deviceprior to the transmission of control data allows the user device toreduce the bandwidth across which is receives signals that may includeuser device payload data to the second bandwidth without having first tohave received signals representing the user device control data.Consequently, the signals representing the user device control data andthe signals representing the user device payload data may be receivedand stored simultaneously.

According to another example embodiment, the user device is configuredto receive user device payload data within a virtual carrier of apredetermined bandwidth, the second bandwidth being approximately equalto the predetermined bandwidth, and the predetermined bandwidth includesa set of the OFDM subcarriers that is substantially similar to the OFDMsubcarriers that form the subset of the OFDM subcarriers included in thesecond bandwidth.

Configuring the second bandwidth to be approximately equal to a virtualcarrier bandwidth allows the repetition of signals to be integrated withthe virtual carrier concept for user devices such as machine typecommunication (MTC) devices. This allows the operation of such devicesto be simplified because it reduces the bandwidth that MTC devicesoperate to receive payload data compared to having a second bandwidthwhich is separate from the virtual carrier.

Various further aspects and features of the present invention aredefined in the appended claims, including but not limited to, aninfrastructure equipment and methods of communicating between a userdevice and an infrastructure equipment

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present disclosure will now be described by way ofexample only with reference to the accompanying drawing in which likeparts are provided with corresponding reference numerals and in which:

FIG. 1 provides a schematic diagram of a wireless communications system;

FIG. 2 provides a schematic diagram of a receiver of a user device ofthe communications system of FIG. 1;

FIG. 3 provides a schematic diagram of LTE subframes;

FIG. 4 provides a schematic diagram of LTE subframes where signalrepetition is implemented;

FIG. 5 provides a schematic diagram of a receiver of a user deviceconfigured to receive repeated signals;

FIG. 6 provides a schematic diagram of LTE subframes where signalrepetition is implemented;

FIG. 7 provides a schematic diagram of LTE subframes where signalrepetition is implemented in accordance with an embodiment of thepresent technique;

FIG. 8 provides a schematic diagram of LTE subframes where signalrepetition is implemented in accordance with an embodiment of thepresent technique;

FIG. 9 provides a schematic diagram of LTE subframes where signalrepetition is implemented in accordance with an embodiment of thepresent technique; and

FIG. 10 provides a schematic diagram of LTE subframes where signalsrepetition and windowed signal reception is implemented in accordancewith an embodiment of the present technique.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS Mobile Communications System

FIG. 1 provides a schematic diagram of a mobile communications system100 for transmitting and receiving data to and from one or more userdevices, where the communications system may for example operate inaccordance with 3GPP Long Term Evolution (LTE). The communicationssystem comprises infrastructure equipment 101 such as a base station orenhanced nodeB (eNodeB) which forms part of a mobile communicationsnetwork and is configured to provide a wireless access interface to oneor more user devices 102 103. The user devices 102 103 may for examplebe mobile phones, machine type communication (MTC) devices such as smartmeters or information aggregation devices in cars or medical devices, ortablet computers. Within the wireless access interface theinfrastructure equipment transmits signals representing the data to theone or more user devices. In FIG. 1 user devices 103 provides an exampleof a smart meter located in the basement of a house. The infrastructureequipment 101 is communicatively linked via communication link 104 to acore network 105 which may in turn be linked to further infrastructureequipment 106 and other communications networks and systems, where thefurther infrastructure equipment may itself be linked to one or moreuser devices 102.

In examples where the system 100 is an LTE system, the wireless accessinterface will be provided in accordance with orthogonal frequencydivision multiplexing (OFDM) where downlink resources are temporallydivided in a plurality of time periods and divided in frequency into aplurality of subcarriers where the subcarriers form in the time domainOFDM symbols that convey signals which represent data to be transmittedto the user devices. The data transmitted to the users devices mayconsist of control plane data and user plane data where the controlplane data coveys control data required by the user devices in order tocommunicate in the downlink (from infrastructure equipment to userdevice) and uplink (from user device to infrastructure equipment) withthe infrastructure equipment, and user plane data conveys user devicepayload data. Further discussion of the wireless access interface ispresented below.

User Device Receiver

FIG. 2 provides a schematic diagram of a simplified receiver that may befound in a user device configured to receive and transmit data in thecommunications system of FIG. 1. In an example where the system 100 isan LTE system, the receiver may for example be an OFDM receiver. Anantenna 201 receives signals transmitted from the infrastructureequipment over a channel and passes them to a baseband converter 202which down converts the received signal to baseband frequencies. Thebaseband signal is then sampled by a sampler 203 at a sampling ratesuitable for the baseband frequencies. A synchroniser 204 is thenconfigured to detect the timing of the control plane data and user planedata before processing of the synchronised signal by a control dataestimator 205 and a payload data estimator 206. The control dataestimator estimates user device control data from signals representingthe control data and provides information to payload data estimatorwhich is required to estimate the user device payload data from thesignals representing the user device payload data. As mentioned above,FIG. 2 provides a simplified OFDM receiver and therefore a number ofelements of an OFDM have not been included. For example, frequencyoffset correction, transformation of the received signal into thefrequency domain for equalisation and data estimation, guard intervalremoval etc. However, the processes performed by these elements andfurther elements may be performed using any suitable processing meansknown in the art.

Downlink Resource Allocation

FIG. 3 provides a simplified example of downlink resource allocation,which may for example being applicable in an LTE system. The downlinkresources are temporally divided into periods referred to as subframes301 where a time period referred to as a radio frame may be formed from10 subframes and the subframes may be 1ms in duration. The downlinkresources are divided in frequency into a plurality of subcarriers,where the number of subcarriers may vary between approximately 128 and2048 dependent upon the bandwidth of the downlink resources, wherepossible downlink bandwidths may include for example 1.25 MHz, 2.5 MHz,5 MHz, 10 MHz, 15 MHz and 20 MHz. Each subframe may be further dividedin time into two 0.5 ms slots where a slot comprising 12 subcarriers maybe referred to as a resource block.

Each subframe includes control or signalling data which may for examplebe transmitted over a physical channel such as a physical downlinkcontrol channel (PDCCH) in LTE, where the control data indicates whichdownlink resources, in terms of subcarriers, slots and timing within thesubframes, have been allocated to each of the user devices currentlybeing served by the infrastructure equipment via the wireless accessinterface. Payload data is transmitted in the downlink over a datachannel such as a physical downlink shared channel (PDSCH) in LTE, wherethe control data indicates to a user device a location in the datachannel in which its payload data will be transmitted and the parametersrequired to estimate the payload data. Payload data may for exampleinclude uplink resource allocations, a request for information from theinfrastructure equipment or information for an application running onthe user device In FIG. 3, three downlink subframes of an LTE system areillustrated where control data is transmitted over the physical downlinkcontrol channel (PDCCH) and user device payload data is transmittedacross the physical downlink shared channel (PDSCH). In an examplereception routine, a user device, such as an MTC device, detects signalsrepresenting control data transmitted across the PDCCH 302 303 at thebeginning of each subframe 301. The user device will then estimate thecontrol data received across the PDCCH of each subframe in orderestablish whether it has been allocated resources in the PDSCH of thecorresponding subframe. If within the control data of the PDCCH there isno indication of user payload data intended for the user device i.e.PDCCH 302, the user device will not attempt to receive signals whichfrom the following PDSCH i.e. PDSCH 304. However, if the estimatedcontrol data indicates to the user device that there is data intendedfor it in the PDSCH i.e. PDCCH 305, the user device will receive signalsthat form the relevant portion 306 of the following PDSCH 307 that thecontrol data has specified, and subsequently estimate the user payloaddata from the received signals. As can be seen from FIG. 3, theresources 306 in the PDSCH allocated to a user device may not extendover all the subcarriers in the subframe and/or over the full temporallength of the PDSCH in the subframe. This, along with the control dataconveyed by signals transmitted across the

PDCCH allows for the allocation of resources in the PDSCH to a pluralityof user devices.

A user device is configured to detect and estimate payload data conveyedin the PDSCH. Accurate detection and estimation of data is dependent ona number of factors, for instance, knowledge of the location of thesignals representing the payload data in a subframe and reception of thesignals representing the user payload data at a sufficient signalstrength and quality. In turn, knowledge of the location of the signalsrepresenting the payload data is dependent upon receiving the signalsacross the PDCCH at a sufficient signal strength and quality so that theuser device control data can be detected and accurately estimated.Consequently, receiving signals representing user device control dataand payload data at a sufficient signal strength are both required inorder to detect and recover payload data in the downlink of an LTEcommunication system or any other equivalent communications system.

During conventional operation of a user device in an LTE network, if theuser device control data cannot be accurately estimated and recoveredfrom the signals transmitted and received across the PDCCH and/or theuser device payload data cannot be accurately estimated and recoveredfrom the PDSCH, the user device data is unable to be received by theuser device. This may occur for example when the channel between theinfrastructure equipment and the user device is highly attenuating thusresulting in highly attenuated signals being received at the receiver.In such a case, the user device may indicate to the infrastructureequipment that the user payload data has or has not been receivedcorrectly via an ACK or NACK message and the infrastructure equipmentwill prepare to resend the payload data. The data may be retransmittedin a subsequent subframe, where each of the instances of the user devicecontrol data and associated payload data are independent from oneanother and may be transmitted in different portions of the PDCCH andPDSCH, respectively. This procedure may be sufficiently robust for userdevices which experience variable channels due to mobility for instance,because poor channel conditions may improve in the near future.Consequently, subsequent transmission(s) of signals representing theuser device control data and payload data may be able to be received ata sufficient strength and quality that the user device control data andpayload data can be accurately detected and estimated. However, in thecase of user devices which are not mobile and/or are unlikely toexperience channel conditions sufficient for reliable detection andestimation of control and or payload data, the above described procedureis unlikely to be sufficiently robust. The use of reduced coding ratesand reduced order modulation schemes may be able to mitigate the effectsof some poor channels, but it is likely that there will still bechannels of poor enough quality that user devices are unable to reliabledetect and estimate control and or payload data from received signals.Furthermore, there may be limits within a system that restrict thecoding rates and modulation orders that may be used. For example, userdevice capabilities, compatibility issues and system parameters may leadto minimum coding rates which are supported by the system, thus limitingthe gains in estimation accuracy that obtained by limiting the codingrate. Furthermore, devices such as MTC devices, which are low complexityand low power, may not have the capability to perform decoding of datawhich has been encoded with complex encoding techniques.

User device 103 of FIG. 1 is an example of a non-mobile user devicewhich may not experience channel conditions sufficient for accuratedetection and estimation of control and or payload data from receivedsignals. As can be seen from FIG. 1, user device 103 is stationary andlocated in the basement of a house and therefore signals representinguser device control data and payload data may be received at a signalstrength and or quality which is not sufficient for accurate datadetection and estimation, even with the use of low codes rates andmodulation orders. Consequently, smart meter 103 provides an example ofa user device where the above described reception routine may beinsufficient to achieve the accurate recovery of user device control andpayload data. As well as user devices in hard to reach locations i.e.basements, user device which are near the border of a cell served byinfrastructure equipment may also experience similar problems due toreception of highly attenuated signals.

Signal Repetition

In order to address the above highlighted deficiencies and problems, ithas been previously proposed that a form of signal repetition may beutilised in order to improve the strength and or quality of the signalreceived at user devices. In particular, when the received signalstrength of a single instance of signals representing data isinsufficient to enable reliable data detection and estimation. Repeatingtransmission of signals representing data provides a more simplearrangement for improving the detection and estimation of communicateddata without significantly increasing processing power requirements andcan be used for low data rate and delay tolerant applications.Furthermore, repetition can use coding, modulation and othercommunications parameters which are determined by a standard, such asLTE, and therefore may be compatible with that standard.

FIG. 4 provides a schematic illustration of a series of subframes wherean example signal repetition procedure is implemented. The principle ofsignal repetition is signals that represent a same instance of controland/or payload data for a user device are repeatedly transmitted by theinfrastructure equipment over one or more subframes or frames. Thesignals may be in a substantially similar position or in substantiallysimilar set of resources of the wireless access interface in each of thesubframes or frames so that they propagate over a substantially similarchannel. However in some examples the repeated signals may betransmitted in different resources in each subframe or frame wheredifferences in channel across which the signals are transmitted aremitigated for example by equalisation. In other examples the signals maybe repeated within a same subframe or frame. The receiver of the userdevice is then configured to receive each of the repeated signals and tostore signals representing the repeated signals in a memory, where thestored signals may take the form of sampled un-demodulated basebandsignals, soft estimates of the data, or hard estimates of the data. Thereceiver then aggregates, accumulates or combines the stored signals, bysummation or averaging for example, so that the relative receivedstrength of the combined signals representing the user device controldata and payload data is increased or additional coding bits areavailable for data estimation and correction. The user device thenproceeds to estimate the control data from the combined signal, wherethe control data indicates the location of the payload data in thecombined signal representing the payload data intended for the userdevice. By the following this procedure it is then possible for theaccuracy of detection and estimation of the user control and payloaddata to be increased. Returning to FIG. 4, signals representing controldata are repeated in the PDCCH 401 of three consecutive subframes. Therepeated signals of the PDCCH 401 which represent control data arestored and then accumulated 402 and the control data intended for theuser device estimated from the accumulated PDCCH at 403. The estimatedcontrol data provides the user device with an indication of the locationin the PDSCH of signals representing the user device's payload data 404.The user device then stores and accumulates the signals received fromthe indicated location 404 of the PDSCH in the next three subframes. Theuser device then recovers an estimate of its payload data from theaccumulated PDSCH signal at 405. In this manner an increased likelihoodof a correct estimation of the payload data can be achieved withoutsubstantially altering parameters of the signals and data such astransmit power, coding rates and or modulation schemes. Accordingly, atransmitter and a receiver performing the above describe repetition canbe compatible with other LTE devices because signal transmissioncharacteristics such as coding rates have not been modified.

FIG. 5 provides a simplified schematic diagram of an example user devicereceiver which is configured to receive repeated data transmissions. Thestructure of the receiver is substantially similar to that illustratedin FIG. 2 but further includes a memory 501 such as a buffer memorywhich is configured to store received repeated signals. The memory 501stores the received signals representing the user device control dataand the payload data, and under the control of a controller 502, passesthe signals to the signal data estimator 205 and the payload dataestimator 206. The signals may be passed to the relevant estimator whena predetermined number of repeated signals have been received or whenthe accumulated signals achieve an amplitude, via summation for example,sufficient to enable reliable detection and estimation of the data to beachieved. However, the exact process by which the received signals arecombined may vary and is discussed in more detail below. The controllermay also be communicatively linked to the other elements of the receiverin order to configure the elements to store and accumulate signals fromthe relevant portions of the PDSCH as indicated by recovered controldata. For example, the controller may require information from thecontrol data estimator in order to configure the receiver to receive andstore signals representing data from appropriate parts of the PDSCH. Thememory 501 may include separate memories for the storage andaccumulation of signals representing the control data the payload dataor other forms of data. Furthermore the configuration of the functionalelements of the receiver may vary depending on the form of repetitionbeing utilised. For example, for repetition techniques where signals arecombined after initial detection and estimation has taken place, anadditional estimator stage(s) may be required or the organisation of thereceiver adapted accordingly.

In order for the repetition structure of FIG. 4 to be implemented, theuser device may require an indication of commencement of the repetitionso that it can begin to store the relevant received signals. However,this may cause problems if the indication signal itself cannot bereceived without repetition. An alternative implementation is toconfigure the memory 501 to be a buffer type memory that stores amaximum number of instances of signals and once the limit is reached,discards the oldest signal instance and stores the most recentlyreceived signal instance. This process can continue for example untilthe accumulated signal reaches a signal strength which is sufficient foraccurate data detection and estimation, thus indicating the buffer ispredominantly made up of the desired repeated signals. This may occurfor example due to the correlation between the repeated signalsrepresenting the user data and the lack of correlation between theportions of the frames or subframes which are not repeated i.e. portionsof the PDCCH which do not apply to the user device and therefore changebetween frames or subframes in which the signals for the user device arerepeated. Another alternative is for the infrastructure to continue torepeat signals until an acknowledgment is received from the user deviceindicating that the data represented by the repeated signals has beenaccurately detected and estimated.

Although, the repetition scheme depicted in FIG. 4 provides a number ofadvantages, there are also associated costs. For example, increasedresources are utilised in order to send data to the user device, wherein FIG. 4 approximately three times the normal resources are utilised totransmit the payload data to the user device. Although this is anobvious disadvantage, it may be mitigated by the fact that communicationinvolving repetition may be predominantly used in off peak periods whereusage of the communications system is low, for example, during thenight. This also fits in with the properties of low cost MTC devicessuch as smart meters which are likely to have delay tolerant data andtherefor transmit data during off peak periods.

In LTE systems, in order to maintain compatibility with legacy LTE userdevices that do not support repetition, there may have to be aone-to-one correspondence between control data indicating where userdevice payload data is located in the corresponding PDSCH and the actuallocation of the payload data. For example, even though the payload datatransmitted in 406 is not detected by the user device, the payload stillhas to be transmitted or the corresponding resources not used by anotheruser device because the control data corresponding to 406 will stillspecify that there is data for the user device in portion 406 of thePDSCH. If this were not the case, it may be possible for the scenariowhere two different portions of the control data specify that payloaddata for two different user devices are at the same location in thePDSCH. The requirement of one-to-one mapping of PDSCH resources to oneuser device therefore results in an inefficient use of downlinkresources. However, in some examples the one-to-one mapping may bebroken by signalling the change prior to the commencement of anyrepetition.

In some examples of signal repetition, in addition to transmittingsignals representing identical control data and payload data for aparticular user device in a substantially identical location in eachframe or subframe, the entirety of the frames or subframes may have tobe repeated in a substantially identical manner. This thereforedecreases flexibility and further reduces efficiency. Furthermore, insome examples where channel conditions or coding rates etc. fortransmitting data to a user device are poor and or high, a large numberof repetitions may be required for a signal of sufficient strength/orsufficient information to be accumulated at the user device.Consequently, because the accumulation of the signals representing thecontrol data and the payload data are not performed concurrently, thedelay in receiving the payload data may be significant. For example, ifa required number of repetitions in terms of subframes is large i.e.100, it may be up to 200 subframes before the payload data can berecovered. In such an example, if the subframes are 1 ms in duration, a200 subframe delay may result in a delay of 0.2 s, which may beunacceptable in some scenarios or to some user devices. Further still,with large repetition numbers user devices may have to be in a receivingmode for a significant period of time as opposed to a reduced powermode, therefore consuming an increased amount of power. This may beparticularly problematic for low power, battery power devices such asMTC devices, whose time spent receiving and transmitting signals shouldbe kept to a minimum if possible.

Repetition has been described in general terms up to this point,however, there are a number of alternative implementations of repetitionand therefore a number of different methods for accumulating andcombining received repeated signals. Two example repetition techniquesare chase combining and incremental redundancy, which may be implementedas part of hybrid ACK procedures. Chase combining includes repeatedlytransmitting a same instance of signals or portions of a same instanceof signals that represent a same instance of data and then combing thesesignals at the receiver either pre or post demodulation. Consequently,chase combining may be viewed as increasing thesignal-to-interference-plus-noise ratio (SINR) of the received signal.Incremental redundancy includes repeating signals which are differentbut represent a same instance of data, for example different codedversions or different code bits of all or part of a same instance ofdata may be transmitted during each repetition. Consequently,incremental redundancy may be viewed as increasing the strength of theerror correction coding at the receiver with the reception of eachrepeated signal. At a user device receiving repeated signals, there area variety of methods that may be used to accumulate or combine thereceived repeated signals. For example, in chase combining storedsampled baseband signals that represent the repeated signals may becombined via equal-gain combining or maximum-ratio combining. Thecombining may also be performed either pre-equalisation orpost-equalisation. In another example, combining of the signals mayoccur once soft or hard decisions have been performed on each of thereceived equalised repeated signals. For instance, an average may betaken over the soft decision from each instance of the repeated signalsand then a hard decision taken to estimate the data. Alternatively, amajority vote system may be employed with hard decisions from each ofthe repeated signals. For incremental redundancy, combining of basebandsignals may not be possible due to the differing repeated signals andtherefore combining of signals representing soft or hard decisions maybe more appropriate.

The aforementioned repetition and combining methods are merely examplesand any suitable methods known in the art may be used. Different methodsof repetition and of combining the received repeated signals each havetheir own advantages and disadvantages. For instance, if sampledbaseband signals are combined, it is the received signals representingthe user device control data and the payload data that are required tobe stored as opposed to the data estimates themselves. Therefore, it issampled versions of portions of the baseband signal that are stored.Storing signals in this manner may require significantly more memorythan storage of signals representing estimates of the underlying data assampling has to be performed at a frequency and with a number ofquantisation levels that are sufficient to achieve a combined signalfrom which control data and or payload data can be accurately detectedand estimated. The actual sampling frequency will be dependent on, amongother things, the baseband frequencies via the sampling theorem, and thenumber of quantisation levels is likely to be dependent on, among otherthings, at least the modulation scheme, coding rates, and the requiredsignal-to-noise ratio (SNR). However, if signals are combinedpost-equalisation and or -post-demodulation, then memory requirementsmay be reduced. In another example, if incremental redundancy isutilised, different coding bits are transmitted with each repetition andso cannot merely be combined via summation. This approach may thereforerequire increased memory compared to chase combining of soft or harddecisions because one symbol in memory corresponds to one receivedsymbol, whereas in chase combing one symbol in memory may be a summationof multiple repeated symbols. In examples where combining of signalsrepresenting the user payload data is performed post-equalisation andafter preliminary soft or hard estimates, it may be required that userdevice control data has already been detected and estimated. The userdevice control data may be required because it includes information onthe location and coding etc. of the user payload data that is necessaryto detect and estimate the user device payload data. Consequently, sucha method may be suited to examples of signal repetition where controldata is received and estimated prior to reception of the repeatedsignals representing the user payload data. With regards to repeatedsignals representing user device control data, estimation of the datacontained therein may be performed at any point after reception,independent of the combining method. This approach is possible by virtueof information on the location of control information in frame orsubframe and any coding of the control data being predefined andtherefore known by the user device prior to reception.

FIG. 6 provides an alternative implementation of signal repetition whichmay decrease the acquisition time of the payload data. In contrast toFIG. 4 where accumulation of signals representing control data andpayload data is done during different subframes, in FIG. 6 whilst thesignals transmitted across the PDCCH 601 are being accumulated all thesignals transmitted across the PDSCH 602 are buffered. Once the locationof the signals representing the user device payload data in the PDSCH isknown and the parameters of the payload data are known, the payload datamay be detected and estimation from the buffered accumulated signal at604. If further accumulation is required after estimation of the controldata, the receiver can store and accumulate only the relevant part ofthe PDSCH signals 605 indicated by the recovered control data. Althoughthis implementation may reduce acquisition delays, it requires asignificant amount of memory in order to store and accumulate all or asubstantial proportion of the signals which represent the PDSCH dataprior to detection and estimation of the user device control data. Inthe case of low cost and reduced power devices such as MTC devices, thismay not be a practical solution.

Narrow Bandwidth Signal Repetition

FIG. 7 illustrates an example embodiment of a repetition procedure inaccordance with the present technique. Repetition of signalsrepresenting user device control data 701, using for example chasecombining or incremental redundancy as previously described, isperformed within the system bandwidth or first bandwidth of the systemin a manner similar to that described with reference to FIG. 4 or 6.However, signals representing the user device payload data aretransmitted using chase combining or incremental redundancy for example,within a predetermined second bandwidth 702 within the PDSCH, where thesecond bandwidth is narrower than the first bandwidth of the system orcurrent subframe and is also within the first bandwidth. The signalsrepresenting the user device payload data may or may not extend acrossthe entirety of the second bandwidth and signals representing payloaddata for other user device(s) may also be transmitted across the secondbandwidth. Consequently, a subset of the subcarriers of the data channelPDSCH are utilised for transmitting the repeated signals representingthe user device payload data. A receiver as illustrated in FIG. 5 maytherefore store and accumulate signals representing the received signalsor the control data contained therein whilst simultaneously storing andaccumulating signals representing received signals or the payload datacontained therein without storing and/or accumulating signalstransmitted across the entirety or a significant portion of the PDSCHbandwidth or first bandwidth. This is in contrast to existing techniquesas previously described with reference to FIG. 6.

In some example embodiments the second bandwidth could be formed by aVirtual carrier arrangement. To support MTC terminals, it has beenproposed to introduce a “virtual carrier” operating within a bandwidthof one or more “host carriers”: the proposed virtual carrier conceptpreferably integrates within the communications resources ofconventional OFDM based radio access technologies and subdividesfrequency spectrum in a similar manner to OFDM. Unlike data transmittedon a conventional OFDM type downlink carrier, data transmitted on thevirtual carrier can be received and decoded without needing to processthe full bandwidth of the downlink OFDM host carrier. Accordingly, datatransmitted on the virtual carrier can be received and decoded using areduced complexity receiver unit: with concomitant benefits such asincreased simplicity, increased reliability, reduced form-factor andlower manufacturing cost. The virtual carrier concept is described in anumber of co-pending patent applications (including GB 1101970.0 [2], GB1101981.7 [3], GB 1101966.8 [4], GB 1101983.3 [5], GB 1101853.8 [6], GB1101982.5 [7], GB 1101980.9 [8] and GB 1101972.6 [9]), the contents ofwhich are incorporated herein by reference.

Once a sufficient number of instances of the repeated signalsrepresenting the control data, and in particular the user device controldata, have been accumulated and combined, the user device control datais detected and estimated 703. In this case, a sufficient number ofinstances may for example refer to accumulating signals until the datacan be detected, until a predetermined number of signals have beenaccumulated, or until the infrastructure equipment ceases repeating therelevant signals. Subsequently, if a sufficient number of repetitions ofsignals representing the user device payload have been accumulated andcombined, the user device payload data is detected and estimated 704from the appropriate location in the accumulated signals from the secondbandwidth. This procedure enables accumulation of the signalsrepresenting the user device payload data to be performed concurrentlywith the accumulation of the signals representing the user devicecontrol data without buffering or storing signals transmitted andreceived across all of or a substantial portion of the PDSCH. Thereforeimprovements in the speed of data acquisition may be achieved comparedto the procedure described with reference to FIG. 4, whilst alsoreducing the memory requirements compared to the procedure describedwith reference to FIG. 6. For example, if the PDSCH is 128 subcarriersin bandwidth and the predetermined bandwidth is 12 subcarriers, the userdevice may require approximately 90% less memory to store signals thatinclude signals representing the user device payload data compared tostoring all signals received from across the first bandwidth or thePDSCH. Consequently, by the use of large numbers of repetitions and useof the reception techniques described above, coverage of a mobilecommunications network may be extended to areas where user devicesreceive a weak signal which would normally not be sufficient forcommunicating with the network, without significantly increasing thememory requirements, costs or battery consumption of the user devices.This may be particularly relevant for battery powered devices such asMTC devices for example which require both their costs and energyconsumption to be reduced and therefore may not be suited to existingrepetition techniques.

In order for a user device to have knowledge of the second bandwidth,additional signalling indicating the second bandwidth may be required tobe transmitted to the user device prior to commencement of repetition,for example, when a user device enters the coverage of an infrastructureequipment such as a base station or eNB. Alternatively, the secondbandwidth may be hardcoded into repetition compatible user devices. Inthe former case, the infrastructure equipment may be configured toselect an appropriate second bandwidth based on for example resourceallocation demands, channel conditions, the number of device requiringrepetition etc. As mentioned above, in some embodiments of the presenttechnique, the second bandwidth may be equivalent to or substantiallysimilar to a predetermined bandwidth of a virtual carrier (VC), whichhas been proposed in order to simplify the operation of MTC devices. Insuch an embodiment a separate second bandwidth in addition to the VC maynot be required and therefore signalling of the second bandwidth may notbe necessary, thus leading to improvements in system efficiency. Inother embodiments of the present technique, the same predefinedbandwidth may be allocated to multiple user devices requiring repeatedsignals. In this case, multiple different signals may be repeated withinthe second bandwidth of each subframe. In further embodiments the secondbandwidth may be defined relative to the first bandwidth or thebandwidth of the PDSCH of each subframe. In such an embodiment thenumber of subcarriers in a radio frame or subframe or even OFDM symbolto OFDM symbol may change without the infrastructure having to re signalthe second bandwidth. For example, the second bandwidth may be definedas subcarriers 36 to 60 or the subcarriers 5/8×S_(t) to 6/8×S_(t) whereS_(t) is the total number of subcarriers. However, regardless of themeans by which the second bandwidth is indicated to the user device,improvements in power consumption and memory requirements can beachieved at the user device when large repetition numbers are utilisedto extend the coverage of a mobile communications network.

In other embodiments, control information required to be received by theuser device may be represented by signals which are transmitted over abandwidth smaller than the first bandwidth or the available bandwidth ofthe subframe. The signals representing user device payload data may alsobe repeated separately from signals representing user device controldata, such as, in systems where a one-to-one mapping from control datato the location of user device payload data is not required. Thisembodiment would therefore further simplify the reception routine of theuser device and the cost and complexity of the user device because itwill be required to operate over a reduced bandwidth.

In some embodiments, due to low coding rates, increased transmissionpower, increased frequency diversity etc., a larger number of instancesof signals representing payload data may be required to be receivedcompared to signals representing control data if the payload data is tobe detected and estimated accurately. For instance, in some networkscontrol data may be transmitted with lower coding rates and lower ordermodulations schemes compared to payload data. FIG. 8 provides anillustration of a repetition procedure in accordance with the presenttechnique where a larger number instances of signals representingpayload data are required to be accumulated compared to signalsrepresenting control data. In FIG. 8, three repetitions of signalsforming the PDCCH 801 and representing user device control data arerequired to be stored and accumulated whereas five instances of thesignals representing the payload 802 data are required. Whilst thesignals received across the PDCCH are being accumulated, knowledge ofthe location of the signals representing the payload data with thesecond bandwidth is unknown and therefore the receiver of the userdevice stores and accumulates signals from the entirety or a significantproportion of the second bandwidth 702 of subframes 803. Once thecontrol data has been detected and estimated from the accumulatedsignals representing the control data, and the location of the signalsrepresenting the payload data known, the receiver commences storing andaccumulating only the signals from the specified location within thesecond bandwidth of frames 804. In some examples, because of the timetaken to estimate the control data from the accumulated and combinedcontrol signals, the receiver may continue to buffer signals from theentirety of the second bandwidth until subframe three of FIG. 8 becauseknowledge of the location of the payload data signals within thepredetermined bandwidth is not known until after the commencement of thePDSCH of frame three.

FIG. 9 provides an illustration of a repetition procedure in accordancewith an example of the present technique where additional controlinformation is transmitted outside of the PDCCH, for example, in anenhanced PDCCH (ePDCCH) in an LTE system. In this case the ePDCCH 901may be located within the second bandwidth 702 so that the user deviceis able to receive the control data represented by signals transmittedover the ePDCCH without having to receive signals transmitted across theentirety or a substantial portion of the first bandwidth. The ePDCCH mayconvey additional control data required in order to detect and estimatethe user device payload data and therefore may be required to bedetected and estimated prior to detection and estimation of the payloaddata in the second bandwidth. Alternatively, the ePDCCH may conveyinformation relating to uplink criteria and therefore should be receivedin a similar manner to signals transmitted over the PDSCH.

As previously described, the user device may require an indication ofwhen signal repetition is set to commence so that the appropriatesignals from the PDCCH and PDSCH can be stored and accumulated. Such anindication may be transmitted at a low code rate and modulation order sothat the probability that it can be received without the need forrepetition is maximised. However, in embodiments where an indication isnot provided or cannot be reliably detected and estimated, a bufferingprocedure as previously described and shown in FIG. 10 may be used. InFIG. 10, buffering of the signals transmitted across the PDCCH and thepredetermined bandwidth 702 begins at 1001. Three instances of thesignals representing the user device control data and payload data arerequired to be accumulated and therefore the next three subframes arethen buffered in the window 1002. The window then moves or slides by onesubframe as each subframe is received as represented by windows 1003 and1004, where a movement of one subframes represents the oldest receivedsignals from a subframe being replaced in the buffer memory by relevantsignals received from the most recent subframe. During the windowrepresented by 1004, three instances of the PDCCH and PDSCH signals thatinclude signals representing the user device control data 1005 andpayload data 1006 have been stored and accumulated. Therefore thecontrol data and the payload data may be detected and estimated, and thecurrent accumulation procedure halted. The point at which a requirednumber of repetitions have been stored may be indicated by theaccumulated signals passing an amplitude threshold for example orsubstantially error-free decoding of the transmitted data.

Although embodiments of the present technique have been described withreference to the physical channels PDCCH and PDSCH of an LTE wirelesscommunications interface, embodiments may also be applied to otherphysical channels of an LTE system, either individually or incombination with other channels. Likewise, although embodiments havebeen described with reference to a LTE systems and wireless accessinterfaces, embodiments of the present technique are not limited to LTEsystems and may be implemented in any systems which have wireless accessresources divided into temporal periods and or resources which may bedivided up for the provision of a multiple access interface. Similarly,different repetition techniques and or combining techniques to thosedescribed above may also be used in conjunction with embodiments of thepresent technique.

Various further aspects and features of the present technique aredefined in the appended claims and various combinations of the featuresof the dependent claims may be made with those of the independent claimsother than the specific combinations recited for the claim dependency.Modifications may also be made to the embodiments hereinbefore describedwithout departing from the scope of the present invention. For instance,although a feature may appear to be described in connection withparticular embodiments, one skilled in the art would recognise thatvarious features of the described embodiments may be combined inaccordance with the disclosure.

The following numbered clauses provide further aspects and examples ofthe present disclosure:

1. A communications system comprising an infrastructure equipment forforming part of a mobile communications network arranged to transmit andreceive data to and from a user device via a wireless access interface,the wireless access interface being provided by the infrastructureequipment using a plurality of Orthogonal Frequency DivisionMultiplexing (OFDM) subcarriers, the plurality of OFDM subcarriersextending across a first bandwidth, and the infrastructure equipment isconfigured

to transmit repeatedly signals representing a same instance of userdevice payload data in a second bandwidth, the second bandwidth beingless than and within the first bandwidth and including a subset of theOFDM subcarriers,

and user device is configured

to receive one or more of the signals repeatedly transmitted across thesecond bandwidth,

to store in a memory signals representing the repeatedly transmittedsignals received across the second bandwidth,

to combine the stored signals, and

to detect the user device payload data from the combined signals, theuser device having been provided with an indication of the secondbandwidth.

2. A communications system according to clause 1, wherein theinfrastructure equipment is configured

to transmit repeatedly signals representing a same instance of userdevice control data in the first bandwidth, the user device control dataproviding an indication of a location of the signals representing theuser device payload data in the second bandwidth, and the user device isconfigured

to receive one or more of the signals representing the user devicecontrol data repeatedly transmitted across the first bandwidth,

to store in the memory signals representing the repeatedly transmittedsignals received across the first bandwidth,

to combine the stored signals representing the repeatedly transmittedsignals received across the first bandwidth, and

to detect the user device control data from the combined signalsrepresenting the repeatedly transmitted signals received across thefirst bandwidth, the detection of the user device payload data from thecombined signals received across the second bandwidth being based on theindication of the location of the signals representing the user devicepayload data in the second bandwidth.

3. A communications system according to clauses 1 or 2, wherein thewireless access interface provided by the plurality of OFDM subcarriersis divided into a plurality of time periods and the repeated signalsrepresenting the user device payload data are transmitted in a same setof resources of the wireless access interface in a first time period andin a second time period.

4. A communications system according to clause 2, wherein theinfrastructure equipment is configured to transmit the indication of thesecond bandwidth to the user device prior to the repeated transmissionsof the signals representing the user device control data.

5. A communications system according to any of clauses 1 to 4, whereinthe user device is configured to receive user device payload data withina virtual carrier of a predetermined bandwidth, the second bandwidthbeing approximately equal to the predetermined bandwidth, and thepredetermined bandwidth includes a set of the OFDM subcarriers that issubstantially similar to the OFDM subcarriers that form the subset ofthe OFDM subcarriers included in the second bandwidth.

6. A communications system according to any of claims 1 to 5, whereinthe communication system operates in accordance with 3GPP LTE.

7. A communications system according to any of clauses 1 to 6, wherein anumber of repeated transmissions of signals representing the user devicepayload data is greater than a number of repeated transmissions of thesignals representing the user device control data.

8. An infrastructure equipment for forming part of a mobilecommunications network arranged to transmit and to receive data to andfrom a user device via a wireless access interface, the wireless accessinterface being provided by the infrastructure equipment using aplurality of Orthogonal Frequency Division Multiplexing (OFDM)subcarriers, the plurality of OFDM subcarriers extending across a firstbandwidth, and the infrastructure equipment is configured

to transmit repeatedly signals representing a same instance of userdevice payload data in a second bandwidth, the second bandwidth beingless than and within the first bandwidth and including a subset of theOFDM subcarriers

9. An infrastructure equipment according to clause 8, wherein theinfrastructure equipment is configured

to transmit repeatedly signals representing a same instance of userdevice control data in the first bandwidth, the user device control dataproviding an indication of a location of the signals representing theuser device payload data in the second bandwidth

10. A method of transmitting and receiving data in a communicationssystem comprising an infrastructure equipment for forming part of amobile communications network arranged to transmit and to receive datato and from a user device via a wireless access interface, the wirelessaccess interface being provided by the infrastructure equipment using aplurality of Orthogonal Frequency Division Multiplexing (OFDM)subcarriers, the plurality of OFDM subcarriers extending across a firstbandwidth, and the method comprising

transmitting repeatedly signals representing a same instance of userpayload data in a second bandwidth from the infrastructure equipment,the second bandwidth being less than and within the first bandwidth andincluding a subset of the OFDM subcarriers;

receiving one or more of the repeatedly transmitted signals across thesecond bandwidth at the user device,

storing in a memory signals representing the repeatedly transmittedsignals received across the second bandwidth at the user device,

combining the stored signals at the user device, and

detecting the user device payload data from the combined signals at theuser device, the user device having been provided with an indication ofthe second bandwidth.

11. A method according to clause 10, the method comprising

transmitting repeatedly signals representing a same instance of userdevice control data in the first bandwidth from the infrastructureequipment, the user device control data providing an indication of alocation of the signals representing the user device payload data in thesecond bandwidth,

receiving one or more of the signals representing the user devicecontrol data repeatedly transmitted across the first bandwidth at theuser device,

storing in the memory signals representing the repeatedly transmittedsignals received across the first bandwidth,

combining the stored signals representing the repeatedly transmittedsignals received across the first bandwidth, and

detecting the user device control data from the combined signalsrepresenting the repeatedly transmitted signals received across thefirst bandwidth, the detection of the user device payload data from thecombined signals received across the second bandwidth being based on theindication of the location of the signals representing the user devicepayload data in the second bandwidth.

12. A method of transmitting data from an infrastructure equipment forforming part of a mobile communications network arranged to transmit andreceive data to and from a user device via a wireless access interface,the wireless access interface being provided by the infrastructureequipment using a plurality of Orthogonal Frequency DivisionMultiplexing (OFDM) subcarriers, the plurality of OFDM subcarriersextending across a first bandwidth, the method comprising

transmitting repeatedly signals representing a same instance of userdevice payload data in a second bandwidth, the second bandwidth beingless than and within the first bandwidth and including a subset of theOFDM subcarriers.

13. A method according to clause 12, the method comprising transmittingrepeatedly signals representing a same instance of user device controldata in the first bandwidth from the infrastructure equipment, the userdevice control data providing an indication of a location of the signalsrepresenting the user device payload data in the second bandwidth.

1: A communications system comprising an infrastructure equipment forforming part of a mobile communications network arranged to transmit andreceive data to and from a user device via a wireless access interface,the wireless access interface being provided by the infrastructureequipment using a plurality of Orthogonal Frequency DivisionMultiplexing (OFDM) subcarriers, the plurality of OFDM subcarriersextending across a first bandwidth, and the infrastructure equipment isconfigured to transmit repeatedly signals representing a same instanceof user device payload data in a second bandwidth, the second bandwidthbeing less than and within the first bandwidth and including a subset ofthe OFDM subcarriers, and user device is configured to receive one ormore of the signals repeatedly transmitted across the second bandwidth,to store in a memory signals representing the repeatedly transmittedsignals received across the second bandwidth, to combine the storedsignals, and to detect the user device payload data from the combinedsignals, the user device having been provided with an indication of thesecond bandwidth. 2: A communications system as claimed in claim 1,wherein the infrastructure equipment is configured to transmitrepeatedly signals representing a same instance of user device controldata in the first bandwidth, the user device control data providing anindication of a location of the signals representing the user devicepayload data in the second bandwidth, and the user device is configuredto receive one or more of the signals representing the user devicecontrol data repeatedly transmitted across the first bandwidth, to storein the memory signals representing the repeatedly transmitted signalsreceived across the first bandwidth, to combine the stored signalsrepresenting the repeatedly transmitted signals received across thefirst bandwidth, and to detect the user device control data from thecombined signals representing the repeatedly transmitted signalsreceived across the first bandwidth, the detection of the user devicepayload data from the combined signals received across the secondbandwidth being based on the indication of the location of the signalsrepresenting the user device payload data in the second bandwidth. 3: Acommunications system as claimed in claim 1, wherein the wireless accessinterface provided by the plurality of OFDM subcarriers is divided intoa plurality of time periods and the repeated signals representing theuser device payload data are transmitted in a same set of resources ofthe wireless access interface in a first time period and in a secondtime period. 4: A communications system as claimed in claim 2, whereinthe infrastructure equipment is configured to transmit the indication ofthe second bandwidth to the user device prior to the repeatedtransmissions of the signals representing the user device control data.5: A communications system as claimed in claim 1, wherein the userdevice is configured to receive user device payload data within avirtual carrier of a predetermined bandwidth, the second bandwidth beingapproximately equal to the predetermined bandwidth, and thepredetermined bandwidth includes a set of the OFDM subcarriers that issubstantially similar to the OFDM subcarriers that form the subset ofthe OFDM subcarriers included in the second bandwidth. 6: Acommunications system as claimed in claim 1, wherein the communicationsystem operates in accordance with 3GPP LTE. 7: A communications systemas claimed in claim 1, wherein a number of repeated transmissions ofsignals representing the user device payload data is greater than anumber of repeated transmissions of the signals representing the userdevice control data. 8: An infrastructure equipment for forming part ofa mobile communications network arranged to transmit and to receive datato and from a user device via a wireless access interface, the wirelessaccess interface being provided by the infrastructure equipment using aplurality of Orthogonal Frequency Division Multiplexing (OFDM)subcarriers, the plurality of OFDM subcarriers extending across a firstbandwidth, and the infrastructure equipment is configured to transmitrepeatedly signals representing a same instance of user device payloaddata in a second bandwidth, the second bandwidth being less than andwithin the first bandwidth and including a subset of the OFDMsubcarriers. 9: An infrastructure equipment as claimed in claim 8,wherein the infrastructure equipment is configured to transmitrepeatedly signals representing a same instance of user device controldata in the first bandwidth, the user device control data providing anindication of a location of the signals representing the user devicepayload data in the second bandwidth. 10: A method of transmitting andreceiving data in a communications system comprising an infrastructureequipment for forming part of a mobile communications network arrangedto transmit and to receive data to and from a user device via a wirelessaccess interface, the wireless access interface being provided by theinfrastructure equipment using a plurality of Orthogonal FrequencyDivision Multiplexing (OFDM) subcarriers, the plurality of OFDMsubcarriers extending across a first bandwidth, and the methodcomprising transmitting repeatedly signals representing a same instanceof user payload data in a second bandwidth from the infrastructureequipment, the second bandwidth being less than and within the firstbandwidth and including a subset of the OFDM subcarriers; receiving oneor more of the repeatedly transmitted signals across the secondbandwidth at the user device, storing in a memory signals representingthe repeatedly transmitted signals received across the second bandwidthat the user device, combining the stored signals at the user device, anddetecting the user device payload data from the combined signals at theuser device, the user device having been provided with an indication ofthe second bandwidth. 11: A method as claimed in claim 10, the methodcomprising transmitting repeatedly signals representing a same instanceof user device control data in the first bandwidth from theinfrastructure equipment, the user device control data providing anindication of a location of the signals representing the user devicepayload data in the second bandwidth, receiving one or more of thesignals representing the user device control data repeatedly transmittedacross the first bandwidth at the user device, storing in the memorysignals representing the repeatedly transmitted signals received acrossthe first bandwidth, combining the stored signals representing therepeatedly transmitted signals received across the first bandwidth, anddetecting the user device control data from the combined signalsrepresenting the repeatedly transmitted signals received across thefirst bandwidth, the detection of the user device payload data from thecombined signals received across the second bandwidth being based on theindication of the location of the signals representing the user devicepayload data in the second bandwidth. 12: A method of transmitting datafrom an infrastructure equipment for forming part of a mobilecommunications network arranged to transmit and receive data to and froma user device via a wireless access interface, the wireless accessinterface being provided by the infrastructure equipment using aplurality of Orthogonal Frequency Division Multiplexing (OFDM)subcarriers, the plurality of OFDM subcarriers extending across a firstbandwidth, the method comprising transmitting repeatedly signalsrepresenting a same instance of user device payload data in a secondbandwidth, the second bandwidth being less than and within the firstbandwidth and including a subset of the OFDM subcarriers. 13: A methodas claimed in claim 12, the method comprising transmitting repeatedlysignals representing a same instance of user device control data in thefirst bandwidth from the infrastructure equipment, the user devicecontrol data providing an indication of a location of the signalsrepresenting the user device payload data in the second bandwidth.14-15. (canceled)